Quiz 2 Key
MA 223
1. Here’s some sampled data: {1,9,2,9,4,5,8}.
(a) (2 points) The sum of the data is 38 and there are 7 points, so the
mean is 38/7. My bad, I meant it to be an integer!
(b) (2 points) The sample variance is
2760
1
((312 + 252 + 242 + 252 + 102 + 32 + 182 )/72 =
.
6
7
√
The standard deviation is
2760/7.
(c) (3 points) Sort the data and obtain {1, 2, 4, 5, 8, 9, 9}. The median
is 5. The bottom half of the data (including the median) is 1, 2, 4, 5
with median 3, so that’s the first quartile. The top half is 5, 8, 9, 9
with median 8.5, so that’s the third quartile.
(d) (3 points) The boxplot should have a box going from 3 to 8.5 with
a line at the median 5. The whiskers should go out to 1 and 9.
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